public class Exer {

	public static void main(String[] args) {
		int sum = 0;
		/*
		for(int i = 1;i<=100;i++){
			if(i % 2 == 0){
				sum += i;
			}
		}
		*/
		int i = 1;
		while(i <= 100){

			if(i % 2 == 0){
				sum += i;
			}

			i++;
		}
		System.out.println(sum);
		


	}

}
